Process for preparing magnetic disk

Abstract

This invention relates to a process for preparing a magnetic disk, which comprises (a) subjecting a substrate having an anodized aluminum film to mirror surface-finishing, (b) widening pores of the anodized aluminum film by chemical dissolution treatment so that the total area of pores becomes from 20 to 80% of the entire surface area, thereby retaining crystalline alumina of the anodized aluminum film extruded after the chemical dissolution treatment, and (c) coating the resultant substrate with a magnetic continuous thin film.

I claim: 
     
       1. A process for preparing a magnetic disk which comprises forming a magnetic continuous thin film on a concavo-convex roughened surface of an aluminum film, said method of forming a magnetic thin film consisting essentially of (a) subjecting a substrate having an anodized aluminum film having a three-layered structure comprising crystalline alumina, amorphous alumina and amorphous alumina containing an acid or alkali ion to mirror surface-finishing, (b) treating the anodized aluminum to chemical dissolution treatment thereby widening pores of the anodized aluminum film so that total area of pores becomes from 20 to 80% of the entire surface area and that the depth of said pores becomes from 50 to 500 Å, thereby retaining crystalline alumina of the anodized aluminum film extruding after the chemical dissolution treatment, whereby a concavo-convex surface is formed on said anodized alumina film and (c) coating said concavo-convex surface resulting from said chemical dissolution treatment with a magnetic continuous thin film directly on said anodized aluminum film subjected to chemical dissolution treatment. 
     
     
       2. The process according to claim 1, wherein said chemical dissolution treatment is electrolytic etching. 
     
     
       3. The process according to claim 1, wherein the substrate is further coated with a carbon layer. 
     
     
       4. The process according to claim 1, wherein the substrate is a glass plate, an aluminum plate or an aluminum alloy plate, having an anodized aluminum film. 
     
     
       5. The process according to claim 1, wherein the magnetic continuous thin film comprises a Co-Cr alloy or a Co-Ni alloy. 
     
     
       6. The process according to claim 1, wherein the anodized aluminum film has a thickness of at least 4 μm. 
     
     
       7. A process for preparing a magnetic disk, which comprises (a) subjecting a substrate having an anodized aluminum film having a (111) crystal face as the predominant face to mirror surface-finishing, (b) widening pores of the anodized aluminum film by chemical dissolution treatment so that the total area of pores becomes from 20 to 80% of the entire surface area, thereby retaining crystalline alumina of the anodized aluminum film extruded after the chemical dissolution treatment, and (c) coating the resultant substrate with a magnetic continuous thin film.